Previous to the revision of the Mass and Office of the Assumption consequent upon the definition of that event as a dogma by Pope Pius XII in 1950, the Epistle of the Feast was as follows, to which I subjoin the commentary of Dom Prosper Guéranger:
Lesson from the Book of Wisdom.
Ecclesiasticus xxiv, 11b-13 & 15-20
In all things I sought rest, and I shall abide in the inheritance of the Lord. Then the creator of all things commanded, and said to me: and he that made me, rested in my tabernacle. And he said to me: Let thy dwelling be in Jacob, and thy inheritance in Israel, and take root in my elect. And so was I established in Sion, and in the holy city likewise I rested, and my power was in Jerusalem: and I took root in an honourable people, and in the portion of my God his inheritance, and my abode is in the full assembly of saints. I was exalted like a cedar in Libanus, and as a cypress tree on mount Sion: I was exalted like a palm tree in Cades, and as a rose plant in Jericho: as a fair olive tree in the plains, and as a plane tree by the water in the streets, was I exalted. I gave a sweet smell like cinnamon and aromatical balm: I yielded a sweet odour like the best myrrh.
The rest that Mary sought is the better part [cf. St Luke x, 42], the repose of the soul in the presence of the King of Peace; and when a soul is thus full of peace, she forms the choicest part of her Lord’s inheritance. No creature has attained so nearly as our Lady to the eternal, unchangeable, peace of the ever-tranquil Trinity; hence no other has merited to become, in the same degree, the resting-place of God.
A soul occupied by active works cannot attain the perfection or the fruitfulness of one in whom our Lord takes His rest, because she is at rest in Him; for this is the nuptial rest. As the Psalm says: ‘When the Lord shall give sleep to His beloved, then shall their fruit be seen.’
Let us, then, who became Mary’s children on the day the Lord first rested in her tabernacle, understand these magnificent expressions of divine Wisdom; for they reveal to us the glory of her triumph. The branch that sprang from the stock of Jesse bears the divine Flower on which rests the fulness of the Holy Ghost; but it has taken root also in the elect, into whose branches it passes the heavenly sap which transforms them and divinizes their fruit. These fruits of Jacob and of Israel – i.e., the works of the ordinary Christian life or of the life of perfection – belong therefore to our Blessed Mother. Rightly, then, does Mary enter to-day upon her unending rest in the eternal Sion – the true holy city and glorified people – the Lord’s inheritance. Her power will be established in Jerusalem, and the saints will for ever acknowledge that they owe to her the fulness of their perfection. ...
The Angelic Doctor says: ‘The trees to which the Blessed Virgin is compared in this Epistle may be taken to represent the different orders of the blessed. This passage therefore means that Mary has been exalted above the angels, patriarchs, prophets, apostles, martyrs, confessors, virgins, and all the saints, because she possesses all their merits united in her single person.’
— Abbot Guéranger, The Liturgical Year, Volume XIII, p.372f.